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United States Patent |
5,629,756
|
Kitajima
|
May 13, 1997
|
Laser beam projection apparatus
Abstract
A laser beam projection apparatus is capable of supplying laser beams
finely converged on an object at all times irrespective of a distance to
the object. The laser beam projection apparatus has a laser beam
generator, including a focus adjusting device, for supplying laser beams
periodically swept within one plane and, at the same time, converged at a
controllable distance, a light receiving element for receiving reflected
laser beams from a predetermined object and generating an output signal, a
distance calculating unit for calculating a distance to the object on the
basis of the output signal and a controller for operating the focus
adjusting device so that the swept laser beams are converged in a position
corresponding to the calculated distance. The controller can change a
sweep speed of the laser beam in accordance with a change in the
calculated distance. The controller cna change a sweep speed of the laser
beam in accordance with a change in the calculated distance.
Inventors:
|
Kitajima; Eiichi (Yokohama, JP)
|
Assignee:
|
Nikon Corporation (Tokyo, JP)
|
Appl. No.:
|
381417 |
Filed:
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January 31, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
356/3.09; 356/4.03; 356/4.08 |
Intern'l Class: |
G01C 003/08; G01C 005/00 |
Field of Search: |
356/3.09,4.08,4.03
|
References Cited
U.S. Patent Documents
4221483 | Sep., 1980 | Rando | 356/250.
|
4830489 | May., 1989 | Cain et al. | 356/73.
|
5110202 | May., 1992 | Dornbusch et al.
| |
5204731 | Apr., 1993 | Tanaka et al.
| |
5258822 | Nov., 1993 | Nakamura et al.
| |
5367458 | Nov., 1994 | Roberts et al. | 364/424.
|
5387969 | Feb., 1995 | Marantette.
| |
5515156 | May., 1996 | Yoshida et al. | 356/3.
|
Primary Examiner: Buczinski; Stephen C.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
What is claimed is:
1. A laser beam projection apparatus comprising:
a laser beam generator, including a focus adjusting device, for supplying
laser beams periodically swept within one plane and, at the same time,
converged at a controllable distance;
a light receiving element for receiving reflected laser beams from a
predetermined object and generating an output signal;
a distance calculating unit for calculating a distance to the object on the
basis of the output signal; and
a controller for operating said focus adjusting device so that the swept
laser beams are converged in a position corresponding to the calculated
distance.
2. A laser beam projection apparatus according to claim 1, further
comprising:
a reflecting member disposed on the object so as to reflect the laser beams
from said beam generator,
wherein said light receiving element receives the laser beams reflected
from said reflecting member.
3. A laser beam projection apparatus according to claim 2, wherein said
reflecting member has at least a pair of reflecting patterns spaced at a
predetermined distance,
said light receiving element periodically generates a couple of output
signals corresponding to the pair of reflecting patterns, and
said distance calculating unit calculates the distance on the basis of a
sweeping period of laser beam and an interval between the couple of output
signals.
4. A laser beam projection apparatus according to claim 3, wherein said
beam generator includes a driving device for sweeping the laser beam
within the plane with a predetermined sweep speed,
said distance calculating unit includes a counter for counting a time
interval between one of the couple of output signals and the other signal
and also a generating period of the couple of output signals, and
the distance to the object is calculated based on a counted value by said
counter and a predetermined interval between the pair of reflecting
patterns.
5. A laser beam projection apparatus according to claim 4, wherein said
laser beam generator further includes a speed controller for controlling
the sweep speed of the laser beam by regulating said driving device, and
said speed controller changes the sweep speed of the laser beam,
corresponding to a change in the calculated distance.
6. A laser beam projection apparatus comprising:
a laser beam generator, including a speed controller, for supplying laser
beams swept at a controllable speed;
a light receiving element for receiving reflected laser beams from a
predetermined object and generating an output signal; and
a distance calculating unit for calculating a distance to the object on the
basis of the output signal,
wherein said speed controller changes a sweep speed of the laser beam,
corresponding to a change in the calculated distance.
7. A laser beam projection apparatus according to claim 6, wherein said
speed controller reduces the sweep speed of the laser beam when the
calculated distance exceeds a predetermined distance.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a laser beam projection
apparatus employed in the sector of construction and civil engineering
and, more particularly, to a laser beam projection apparatus used for
level surveying using a laser beam and a work of marking along a
horizontal or perpendicular surface.
2. Related Background Art
There is known a laser beam projection instrument as disclosed in, e.g.,
U.S. Pat. No. 4,221,483. This laser beam projection instrument includes an
optical system having a collimator lens which substantially collimates the
laser beams emitted from a light source such as an He--Ne gas laser or a
laser diode. The thus collimated laser beams are then emitted in the
horizontal direction via a rotary mirror. Thus, the laser beam projection
instrument supplies the laser beams swept on the horizontal plane.
This type of conventional laser beam projection instrument is placed
substantially at the center of a room, and the swept laser beams are
emitted, thereby making it possible to perform leveling on an inner wall
surface. That is, if the laser beams are visible, a line of the laser beam
appears on the peripheral wall surface, and, therefore, the worker puts a
mark on the center of the line width. Whereas if invisible, a dedicated
sensor is mounted on the wall surface, and the marking may be effected.
Such a marking operation is executed at a predetermined interval along the
line of laser beams, and thereafter the respective marks are connected by
a line, thus completing the leveling operation.
Further, as disclosed in U.S. Pat. No. 4,830,489, there is also known an
alignment apparatus using the laser beam projection instrument in
combination with one or a plurality of sensors.
If a distance from the laser beam projection instrument to the wall surface
or the sensor is long, however, a width of the laser beams emitted from
the conventional laser beam projection instrument is gradually expanded.
Consequently, there arises a problem in which the line of the laser beams
becomes thick enough to induce a deterioration in terms of a marking
accuracy. Further, in the case of the visible laser beams, there is caused
such a problem that a luminance on the wall surface decreases with the
expansion of the beam width or an increase in a beam shifting speed on the
wall surface, resulting in a worsened visual recognizability.
Hitherto, there has been also proposed a laser beam projection instrument
incorporating a function of manually control the optical system so that
the laser beams are converged on an object such as a wall surface or the
like. There exists, however, a problem in which two workers are needed for
controlling the optical system and for confirming the width of the laser
beams on the wall surface, and, besides, the work is conducted while the
two workers communicated with each other, resulting in a worsened
workability.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a laser beam
projection apparatus capable of supplying laser beams controlled in the
best state at all times irrespective of a distance to an object.
It is another object of the present invention to provide a laser beam
projection apparatus which enables only one worker to perform a marking
operation.
According to one aspect of the present invention, there is provided a laser
beam projection apparatus comprising: a laser beam generator, including a
focus adjusting device, for supplying laser beams periodically swept
within one plane and, at the same time, converged at an controllable
distance; a light receiving element for receiving reflected laser beams
from a predetermined object and generating an output signal; a distance
calculating unit for calculating a distance to the object on the basis of
the output signal; and a controller for operating the focus adjusting
device so that the swept laser beams are converged in a position
corresponding to the calculated distance.
According to the laser beam projection apparatus of the present invention,
the laser beams are always finely converged on an object, and, hence, a
clear-cut line is projected on the object.
A reflecting member is disposed on the object so as to reflect the laser
beams from the laser beam generator, and the reflecting member is formed
with at least one pair of reflecting patterns spaced at a predetermined
interval. Since the light receiving element periodically generates a
couple of output signals corresponding to the pair of reflecting patterns,
the distance calculating unit is capable of calculating a distance R on
the basis a sweep period of the laser beam and the interval between the
couple of output signals.
If the laser beam generator is further provided with a speed controller for
controlling the sweep speed of the laser beam by regulating the driving
device, it is possible to perform the control of reducing the sweep speed
of the laser beam in accordance with an increase in the calculated
distance R. For example, if the calculated distance R exceeds a fiducial
distance, the sweep speed is reduced. Whereas if the distance R is the
fiducial distance or under, the control is effected to increase the sweep
speed. A visual recognizability of the line on the object is thereby
enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become apparent
during the following discussion in conjunction with the accompanying
drawings, in which:
FIG. 1 is a vertical cross sectional view illustrating a laser beam
projection apparatus in an embodiment of the present invention;
FIG. 2 is a plan view showing a light reflecting plate in the embodiment of
the present invention;
FIG. 3 is a block diagram illustrating an embodiment of a control device;
FIG. 4 is a diagram showing a waveform of an output signal of a light
receiving element;
FIG. 5 is an explanatory view illustrating a using state in a marking
operation by use of the laser beam projection apparatus in the embodiment
of the present invention; and
FIG. 6 is a partially enlarged view of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of a laser beam projection apparatus of the present invention
will be discussed. A laser beam projection apparatus illustrated in FIG. 1
includes a light projection unit 1 and a leveling unit 2.
A housing 3 of the light projection unit 1 houses a laser diode for
emitting a visible laser beam L. A projection lens 5 for converging the
visible laser beams L is so disposed upwardly of the laser diode 4 as to
be held by a support member 13. A beam splitter 6 is provided upwardly of
the projection lens 5. A condenser lens 7 is disposed in the left
direction of the beam splitter 6. A light receiving element 8 is fixed in
a focal position of the condenser lens 7.
A rotary cylindrical body 9 is placed above the beam splitter 6. The rotary
cylindrical body 9 is so supported by the housing 3 as to be rotatable
about a perpendicular axis through a bearing 10. A motor 12 for rotating
the rotary cylindrical body 9 through a transmission belt 11 is provided
in the left direction of the light receiving element 8. A pair of reflex
mirrors 14a, 14b for guiding the laser beams L penetrating the projection
lens 5 and the beam splitter 6 in the horizontal direction are fixed
within the rotary cylindrical body 9.
The rotary cylindrical body 9 is formed with an aperture portion 9a which
admits the laser beams L traveling in the horizontal direction from the
reflex mirror 14b. On the other hand, a multiplicity of aperture portions
3a through which the laser beams L from the aperture portion 9a are
emitted to the outside are formed along a substantially entire periphery
of the housing 3. Transparent protection glasses 27 are fixed to these
aperture portions 3a. The rotary cylindrical body 9 is rotated by the
motor 12, and the laser beam L penetrating the protection glass 27 and is
emitted to the outside is swept through 360.degree. within the horizontal
plane.
Further, the support member 13 is fitted to a cylindrical linear guide 19
so that the projection lens 5 is precisely shiftable along the optical
axis of the laser beam L leading to the reflex mirror 14a from the laser
diode 4. The linear guide 19 has a guide notch 19a formed in the axial
direction. The support member 13 fitted to the linear guide 19 is
precisely guided along the optical axis of the laser beam L through the
notch 19a. The support member 13 is also fitted to a ball screw 21 so
supported by the housing 3 as to be rotatably through bearings 20a, 20b. A
gear 22 is fixed to one end of the ball screw 21 and meshes with a gear 24
of a pulse motor 23.
The leveling unit 2 is constructed of an upper plate 15 fixed to the
housing 3 of the light projection unit 1 and a lower plate 18 attached via
three pieces of leveling screws 17 to this upper plate 15.
A resinous light reflecting plate 30 for reflecting the laser beam L
emitted from the light projection unit 1 is disposed above an object for
marking. As illustrated in FIG. 2, reflecting patterns 31, 32 spaced at a
predetermined interval D but parallel to each other are formed on the
light reflecting plate 30. Each of the reflecting patterns 31, 32 has a
strong directivity to reflect the laser beam L in an incident direction
and is constructed of, e.g., a reflecting sheet the surface of which is
formed with a multiplicity of hyperfine corner cubes. The light reflecting
plate 30 includes a line 33 extending orthogonally to the reflecting
patters 31, 32. marking notches 34a, 34b are formed in positions at both
ends of the line 33.
The light projection unit 1 is equipped with a control device shown in FIG.
3. The laser diode 4 emits the visible laser beam L on the basis of a
drive signal given from a controller 25 including an arithmetic unit. An
output of the light receiving element 8 enters a time counter 26, while an
output of the time counter 26 enters the controller 25. The light
receiving element 8 receives and photoelectrically converting the laser
beams reflected by the light reflecting plate 30, thereby generating
consecutive pulse couplings (P11), P12), (P21, P22), . . . as illustrated
in FIG. 4. The time counter 26 counts a time interval t between the pulses
P11 and P12 and a time interval T between the pulse coupling (P11, P12)
and the pulse coupling (P21, P22). The controller 25 calculates a distance
from the light projection unit 1 to the light reflecting plate 30 on the
basis of an item of time data counted by the time counter 26. The
controller 25 then outputs a drive pulse to a pulse motor 23 and, at the
same time, controls a rotating speed of the motor 12.
The pulse motor 23 rotates in response to the drive pulse from the
controller 25, thus moving the support member 13 for holding the
projection lens 5. As a result, a converging position of the laser beams L
is adjusted. The rotating speed of the motor 12 is controlled by the
controller 25, thereby determining a sweep speed of the laser beam L.
There is given an explanation of the operation when performing the marking
along the horizontal plane on a wall surface within a room by use of the
laser beam projection apparatus in this embodiment with reference to FIGS.
5 and 6.
The light projection unit 1 mounted on a tripod is placed substantially at
the center of the room. After the leveling has been performed by operating
the leveling unit 2, the light projection unit 1 is started. With the
start-up of the light projection unit 1, the controller 25 outputs a
lightening signal. Hereupon, the laser diode 4 emits the laser beams L.
The laser beams L are converged by the projection lens 5 and are reflected
by the pair of reflex mirrors 14a, 14b in the horizontal direction.
When starting the motor 12, the rotary cylindrical body 9 is rotated
clockwise, and, therefore, the laser beams L penetrating the protection
glasses 27 and emerging therefrom toward the outside are swept through
360.degree. within the horizontal plane. These laser beams L are so
initialized as to be converged at a distance of 30 m from the light
projection unit.
A line 28 of the laser beam having a width a, upon sweeping the laser beam
L, appears on a wall surface 29, and, hence, the worker perpendicularly
places and holds the light reflecting plate 30 on the line 28 so that the
reflecting patterns 31, 32 are substantially orthogonal to the line 28. On
the occasion of this placing operation, if a line 33 orthogonal to the
reflecting patterns 31, 32 is overlapped with the line 28 of the laser
beam, the light reflecting plate 30 can be correctly perpendicularly
placed.
When the light reflecting plate 30 is disposed on the wall surface 29, the
reflecting patterns 31, 32 are periodically repeatedly swept by the laser
beams L. When irradiating the reflecting pattern 31 with the laser beams
L, the laser beams reflected therefrom travel back to the light projection
unit 1 and are converged on the light receiving element 8, with the result
that pulses P11 are outputted from the light receiving element 8. Upon
receiving these pulses P11, the time counter 26 starts counting these
pulses.
The laser beams L are rotated, and, when the reflecting pattern 32 is
irradiated with the laser beams L, the light receiving element 8 outputs
pulses P12 after photoelectrically converting the reflected laser beams.
The time counter 26 counts the time t from a point of time when receiving
the previous pulse P11 to a point of time when receiving the pulse P12 and
outputs an item of time data thereof to the controller 25.
Next, when the laser beam L makes one rotation and again falls on the
reflecting pattern 31, the light receiving element 8 outputs a pulse P21.
The time counter 26 counts a time T from a point of time when receiving
the former pulse P11 to a point of time when receiving the latter pulse
P21 and outputs an item of time data thereof to the controller 25.
Thus, the controller 25 obtains the time for which the laser beam L travels
across between the reflecting patterns 31 and 32 and the time T for which
the laser beam L makes one rotation. Then, the following proportional
formula is established:
D/2.pi.R=t/T
where D is the interval D between the reflecting patterns 31 and 32, and R
is the distance from the center of the light projection unit 1 to the
light reflecting plate 30. Hence, the controller 25 performs a calculation
such as: Distance R=DT/2.pi.t. Then, the following relationship is also
established:
1/F=1/f1+1/R
where F is the focal length of the projection lens 5, f1 is the distance
from the light source 4 to the projection lens 5, and R is the distance
from the projection lens 5 to an image of the light source. Therefore, the
controller 25 obtains a position of the light source 4 in accordance with
the following formula:
f1=F.multidot.R/(R-F)
Then, the controller 25 calculates a direction and a quantity with which
the projection lens 5 should be shifted from the initialized position.
The controller 25 outputs, to the motor 23, the pulses the number of which
corresponds to the thus calculated shift quantity, thereby rotating the
pulse motor 23. With rotations of the pulse motor 23, a ball screw 7 is
rotated through gears 24, 22, and the projection lens 5 is thus shifted
together with the support member 13. The converging position of the laser
beams L coincides with the calculated distance R, i.e., on the wall
surface 29.
Further, the controller 25 determines a dimension of the calculated
distance R and changes the rotating speed of the motor 12 in accordance
with the distance, thus adjusting a sweep speed of the laser beam. If an
angular speed of the rotating laser beam is fixed, the sweep speed of the
laser beam increases with the larger distance R, with the result that a
visual recognizability of the laser beam projected on the wall surface
declines. For this reason, when the distance R is large, the decline in
terms of the visual recognizability is prevented by reducing the angular
speed of the rotating laser beam. For example, if the distance exceeds the
initialized value of 30 m, the rotating speed of the motor 12 is
decreased. Contrastingly, if equal to 30 m or under, the rotating speed is
increased, thus controlling the rotating speed.
As a modified example of the light reflecting plate 30 in this embodiment,
one reflecting pattern having a width D may be used in place of the two
reflecting patterns 31, 32 spaced at the interval D but parallel to each
other. In this case, the time counter 26 detects a time for which the
laser beam L travels across from one edge of the reflecting pattern to the
other edge thereof.
A light wave distance measuring technology which has hitherto been known in
the field of surveying may be employed for obtaining the distance R to the
wall surface. For instance, the pulse beam is emitted toward the wall
surface, and a distance can be also obtained by measuring a time for which
the pulse beam returns. Alternatively, there may be used a distance
detecting technology known in the field of cameras.
For changing the converging position of the laser beams, there may be taken
such a construction that the projection lens is fixed, and the light
source is moved with respect to the projection lens.
The line 28 of the laser beam thus finely clearly appears on the wall
surface, and, therefore, the worker is capable of making the line 28
precisely coincident with the line 33 of the light reflecting plate 30 and
putting a mark on the wall surface 29 by making use of the marking notches
34a, 34b formed at both ends of the line 33.
It is apparent that, in this invention, a wide range of different working
modes can be formed based on the invention without deviating from the
spirit and scope of the invention. This invention is not restricted by its
specific working modes except being limited by the appended claims.
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